looking at these fuel pumps and trying to figure out what they mean by "(use with inline check valve)" ? scroll down a bit and there's two types of fuel pump for the same model... heres the link
www.crowleymarine.com
Mariner Outboard 1990 75 [ELHPTO] 7075411SD [7075411SD] - Parts Lookup | Crowley Marine
View parts diagrams and shop online for 7075411SD : Mariner Outboard 1990 75 [ELHPTO] 7075411SD. Offering discount prices on OEM parts for over 50 years. FAST $4.95 shipping available.
www.crowleymarine.com